The present invention relates to a method for the formation of a silicon oxide film on the surface of a substrate. More specifically, the present invention relates to a method for the formation of a thick silicon oxide film that is free of cracks and pinholes and that is insoluble in organic solvents.
The formation of a protective film on the surface of a substrate is a technique in general use for the protection of the surface of a substrate. In the particular case of the electric/electronic industries, there has been a very substantial increase in the complexity of semiconductor devices and in topographical variations on the surface of semiconductor devices in association with recent increases in the degree of integration and layer count of such devices. An interlevel dielectric layer may be formed on the surface of a semiconductor device in order to planarize the topographical variations on the surface of the device, while a passivation coating can be laid down on the surface of a semiconductor device in order to protect it from mechanical damage, chemical damage, damage due to static, ionic contaminants, nonionic contaminants, radiation damage, and so forth.
Silicon oxide films are typically used for the interlevel dielectric layers and passivation coatings formed on semiconductor device surfaces. Chemical-vapor deposition (CVD) and spin-coating are examples of the methods used to form these silicon oxide films. In one such spin-coating method, a film of hydrogen silsesquioxane resin is formed on the surface of the substrate (e.g., the semiconductor device, etc. ), and the resin film-bearing substrate is then heated to 500.degree. C. to 1,000.degree. C. in an inert gas atmosphere in order to form a silicon oxide film (Japanese Patent Application Laid Open [Kokai or Unexamined] Number Hei 3-183675 [183,675/1991]).
However, the method proposed in Japanese Patent Application Laid Open Number Hei 3-183675 is not able to produce a silicon oxide film thicker than 0.6 micrometers (6,000 angstroms). As a result, this method cannot completely planarize the topographical variations encountered on the surfaces of semiconductor devices, i.e. , topographical variations or height differences in excess of 0.6 micrometers (6,000 angstroms). In addition, when the production of a thick silicon oxide film is attempted by this method, cracks and pinholes are produced in the silicon oxide film and the reliability of the semiconductor device is drastically reduced.
The inventors conducted extensive research into the cause of the inability of the method proposed in Japanese Patent Application Laid Open Number Hei 3-183675 to produce thick silicon oxide films. It was discovered that this inability is due to the excessively high-temperature heating (500.degree. C. to 1,000.degree. C.) that is used in order to give a 0% content of silicon-bonded hydrogen in the silicon oxide product. It was also discovered that the silicon oxide film could perform well as an interlevel dielectric layer or passivation coating on the surface of a semiconductor device when the Si-bonded hydrogen content in the silicon oxide film product did not exceed 80% of the Si-bonded hydrogen content in the starting hydrogen silsesquioxane resin. Accordingly, the present invention was achieved as a result of extensive research into a silicon oxide film formation method that would be capable of producing a crack-free and pinhole-free thick silicon oxide film that could function as an interlevel dielectric layer or passivation coating on tile surface of a semiconductor device and that would also be able to thoroughly planarize the topographical variations on the surfaces of semiconductor devices.
The present invention takes as its object the introduction of a method for the formation of an organic solvent-insoluble, crack-free and pinhole-free silicon oxide thick film by the formation of a hydrogen silsesquioxane resin film on the surface of a substrate and then heating this resin film-bearing substrate.